RU2402148C1 - Inductor motor control method - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: in control method of inductor motor there preliminarily entered to the memory of control system is table dependence Δi_Φ on position (turning angle) of rotor, ratio of priority of phase switching at direct (forward movement) and reverse (backward movement) direction of rotor rotation, parametres are measured and compared to table ones, mark signals are supplied, optimum operating phase is determined as per the table of priority of phase switching at zero rotation frequency as per the ratio of amplitudes of mark signals of fixed length to all phase windings and the specified rotation direction. Moments of beginning of current rise are determined as functions of amplitude of mark signals at rotation frequency of 0 to n_gen. : t_open=f(Δi_{Φ max}), where Δi_{Φ max} - maximum mark signal to non-operating phase; t_open - moment of opening of current phase, which is measured with the number of beats of microprocessor timer; fixed length and frequency restricted with winding inductance of inductor motor, operating frequency of transistors of independent voltage inverter and quick operation of control system, and completion moments of supplied current to the phase are determined from the opening moments of current and previous phases in compliance with the function specified in invention formula, and at rotation frequencies n>n_gen there determined are completion moments of supplied current to phase windings as function t_close=f(di_Φ/dt), where di_Φ/dt - derivative of phase current at transition to generation mode; and beginning moments of current formation in phase are determined in compliance with the function specified in invention formula.

EFFECT: improving control reliability of inductor motor within the whole range of rotation frequencies and effectiveness of electric drive owing to simplifying its design.

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Description

The invention relates to the field of electrical engineering, namely to control a jet induction motor (ID).

A known method of controlling an induction motor (see US patent No. 4616165). This source describes an induction motor with a control system that implements a method consisting in the formation of currents in the phase windings of the motor by applying voltage pulses to the winding inside each period of the model of the rotor position sensor (DPR), the time intervals determining the moments of the beginning and end of voltage supply, are set as functions of the engine speed in a tabular manner. The disadvantage of this method is the limited scope that allows you to use this method only to control the induction motor when tuning to one or more operating modes.

The method of controlling a jet induction motor (see RF patent No. 2260243) allows to minimize the error of the moments of turning on and off the phases of the motor, but it uses a direct determination of the position of the rotor using the DPR, which complicates the design of the sensors.

In the article by Lisovsky A.A., Semenov I.M. "Sensorless valve-inductor electric drive for extreme conditions" (materials of the XV scientific and technical conference "Extreme Robotics" on April 6-7, 2004, the State Scientific Center of Russia, the Central Research Institute of Robotics and Technical Cybernetics) describes several methods for indirectly determining the position of the rotor. One of them is a method of calculating the current flux linkage and comparing it with a table value. To implement this method, it is necessary to apply test sinusoidal signals of high frequency to the phases of the motor. The method provides starting the engine and its operation in the entire range of rotational speeds, but requires complicating the hardware of the drive and the use of faster microcontrollers in the control system.

In the article Arakelyan A.K., Gluhenkogo T.G. “Determining the position of the rotor in high-speed sensorless valve-induction electric drives” (Journal of Electricity No. 4/2003), the current-gradient method (TGM) is considered, the main idea of which is to determine the angle of rotation of the rotor θ at which the partial derivative of the phase current di / dθ begins to change, which corresponds to the beginning of the overlap of the poles of the rotor and stator or the exit from the blocked state. The disadvantage of this method is the inability to determine the position of the rotor in a stationary state. In addition, TGM cannot be implemented when algorithms are used to control the pulsations of the electromagnetic moment of the engine.

There are many other algorithms for determining the switching times with or without diagnostic signals. When using modern DSP controllers, vector ID control is possible. All these algorithms are effective only for a certain range of speeds of the induction motor. In order to ensure stable drive control over the entire speed range, it is necessary to use combined methods, taking into account the nature of the load and the capabilities of the microprocessor control system.

The closest in technical essence is the method of controlling the induction motor (see RF patent No. 2182743), which consists in the fact that unipolar voltage pulses (current packages) are supplied to the motor winding. The magnetization curve of the electric motor is preliminarily determined and stored at a given switching angle, switching from one phase winding to another is carried out, for which the instantaneous current value and the instantaneous voltage value in it are determined. Based on the obtained values, the instantaneous value of flux linkage is calculated, compared with the set value and, at the moment of their coincidence, a signal is generated to turn off the working phase winding and turn on the next one, for which the process is repeated, then determine the current value of the winding resistance and use the obtained value as the calculated value of the winding resistance, at this is to determine the current value of the resistance of the winding pre-measure the resistance value of the winding and its temperature in the cold state, the obtained values are remembered, by the measured instantaneous value of the current in the winding, the losses in the electric motor are determined, the current value of the ambient temperature is determined, the overheating temperature of the winding is calculated from the thermal model of the electric motor, summed with the current value of the ambient temperature, the current value of the winding resistance is determined from the summation according to dependency

RT = R0 (1 + T) / (1 + T0),

where R0 is the resistance of the winding in the cold state;

T0 is the ambient temperature with a change in R0;

1 - temperature coefficient of resistance of the material of the winding;

T is the temperature of the winding in a heated state.

To implement the method described above, the phase current and phase voltage sensors for each phase winding of the motor are used as feedback in the control system, which complicates the design of the drive and the control system. In addition, calculating the instantaneous value of flux linkage and comparing it with tabular values requires a large amount of memory and processor time, which negatively affects the accuracy of determining the switching moments. Therefore, to implement sustainable control at high engine speeds, the use of high-speed controllers is necessary.

The objective of the invention is to increase the reliability of controlling the induction motor in the entire range of rotational speeds and the efficiency of the electric drive by simplifying its design.

The problem is solved by the control method of the induction motor, in which the control system preliminarily stores the tabular dependence Δi _f on the angle of rotation of the rotor, the dependence of the sequence of phase switching for the forward (forward) and reverse (reverse) direction of rotation of the rotor, which introduced the differences:

at zero speed, the optimal working phase is determined from the ratio of the amplitudes of the current packages of a fixed duration to all phase windings and a given direction of rotation according to the phase sequence sequence table, and at the rotation frequency n <n _gene . moments of the beginning of the formation of current t _open. determined as a function of the amplitude of the current packages Δi _{f of a} fixed duration Δt and the frequency limited by the inductance of the ID winding, the operating frequency of the transistors of the autonomous voltage inverter (AIN) and the speed of the control system according to the formula:

t _open = f (Δi _{f max} ),

where t _open - the moment of the beginning of current formation, measured by the number of clock cycles of the microprocessor timer (1 clock is 0.8 μs);

Δi _f - the amplitude of the current package.

In this case, the moment of the end of the current supply to the phase t _closed. determined from the moment of opening the current and previous phases according to the formula:

where t is _closed - the moment of the end of the current supply to the phase;

t _{open 1} - the moment of the beginning of formation of the current of the current phase;

t _open - the moment of the beginning of the formation of current of the previous phase, measured by the number of clock cycles of the microprocessor timer (1 clock is 0.8 μs).

At rotation frequencies n> n _gene. where n is the _gene. - the rotation frequency at which the current increases during the transition of the phase to the generator mode, the moments of the end of the current supply to the phase windings t _closed. determined as a function of changing the sign of the derivative of the phase current di _f / dt upon transition to the generation mode (Fig.6). The moment of the beginning of the formation of current in the phase is determined by the formula (figure 2):

where t is _closed - the moment of the end of the current supply to the phase windings of the previous phase;

t close ₁ - the moment of the end of the current supply to the phase windings of the current phase.

A positive result of the use of the proposed method of controlling the induction motor is to increase the reliability of controlling the induction motor in the entire range of rotational speeds and the efficiency of the electric drive by simplifying its design due to the refusal to use voltage sensors and temperature sensors used in the prototype.

Figure 1 shows a device for implementing the proposed method.

Figure 2 shows the change in the amplitude of the current packages Δi _f in all phases of a three-phase motor during rotation with a low frequency (from 0 to n <n _gen. ) Clockwise and counterclockwise. For comparative evaluation, the signals corresponding to the phases are shown.

Figure 3 shows a graphical representation of the table recorded in the memory of the control system for determining the position of the rotor of the induction motor at start-up.

Figures 4 and 5 show diagrams of switching the phase windings of the motor during clockwise and counterclockwise rotation.

Figure 6 - the closing moments of the working phases at engine speeds n> n _gene. .

7 is an algorithm that implements a control method.

The method of controlling the induction motor is carried out using the device shown in Fig. 1 in the form of a functional diagram of a sensorless induction drive and containing an autonomous voltage inverter 1 (AIN) supplying the induction motor 2 (ID), phase current sensors 3 are installed at the input of the motor 2, which connected to the phase sequence determining unit 4 (BOOF), to the rotor speed determining unit 5 (BOC) and the phase current regulator 6 (RT). The indicated blocks 4, 5, 6 are connected by outputs to the control pulse distributor 7 (RIU), RT 6 is connected to the task unit (BZ) 8, the input of which is connected to the CAN interface 9, and the output is connected to the RIU 7, which in turn is connected to AIN 1. The output of the unit BOC 5 is connected to the input of the BOOF 4. BOC 5, BOOF 4 and RT 6 are interconnected. BZ 8, RIU 7, BOCH 5, BOOF 4, RT 6 can be parts (elements) of the microcontroller 9, for example C167 / ST10.

The method is implemented as follows. At zero engine speed, the position of the rotor (angle of rotation) is determined from the amplitude of the current packages of a fixed duration in all phases of the engine (see figure 2) and the direction of a given rotation. The tabular dependence of Δi _f on the angle of rotation of the rotor θ ID 2 for the full phase period (see Fig. 3) is previously stored in the memory of the control system 9. In addition, the memory of the control system 9 is recorded the sequence of phase switching for forward (forward) and reverse (backward movement) the direction of rotation of the induction motor (see figures 4, 5). Since starting is possible both with a cold and a hot engine, the characteristic Δi _f (θ) (see Figs. 2, 3) is used to qualitatively evaluate all three phase current packages and determine the optimal working phase only at zero engine speed. The ratio of the read amplitude Δi parcels _fA, Δi _vWF, Δi _fs corresponds strictly definite angle of rotation of the rotor. For a given direction of rotation, the optimal working phase is determined from the phase sequence tables. Further phase switching is carried out on the basis of the analysis of the amplitude of the current packages (the phase that enters into operation), a table of the sequence of phase switching depending on the direction of rotation and speed n ID 2.

In BOOF 4, depending on the rotation speed n, the control mode of ID 2 is determined and, accordingly, for n <n, the _gene. determine the moments of inclusion by the expression

t _open = f (Δi _{f max} ),

where Δi _{f max} is the largest current sending to the idle phase of a fixed duration and frequency limited by the inductance of the winding of the induction motor 2, the operating frequency of the transistors of the autonomous voltage inverter 1 and the reaction of the control system (speed) 9, or turning off the next phases of the motor according to the expression

where t is _closed - the closing moment of the current phase, measured by the number of clock cycles of the microprocessor timer (1 clock is 0.8 μs);

t _open - the moment of opening the current phase;

t _{open 1} - the moment the current switching starts in the previous phase winding,

which go to RIU 7.

Acceptable accuracy of phase switching with this method of control regulation (1-3 electric degrees) at an acceptable switching frequency of power devices of an autonomous voltage inverter 1, for example 1 kHz, can be achieved only at a rotation frequency n <n _gene. motor 2 due to the need for dead time pauses for dying current pulses to zero. In addition, current transmissions into the out of phase phase lead to additional pulsation of the motor 2 moment. At rotation frequencies n> n _gene. determine the moments of the end of the current supply to the phase windings as a function of t _closed. = f (di _f / dt), where di _f / dt is the derivative of the phase current upon transition to the generation mode, and the moments of the onset of current formation in the phase are determined as

where t is _closed - the moment of closing the current phase;

t _open - the moment of opening the current phase;

t close ₁ - the closing moment of the previous phase.

The RT 6 _fA phase currents i, i _vWF, i _fs is compared with a predetermined current value i _backside. , and if the latter is exceeded, the blocking signal (Bloc.) is supplied to the RIU 7. Control signals (start, stop) via the optically isolated CAN interface after conversions to the BZ 8 are also digitally transmitted (Mode) to the RIU block 7. Also in block RIU 7 signal F - the order of inclusion of the phases. In RIU 7 analyze the input signals (Dir., N, F and Blk.) And form control pulses for the corresponding keys AIN 1.

At a speed n> n _gene. the determination of the phase switching moments is performed by the motor-generator method, based on the phenomenon of an increase in the winding current during the phase transition to the generator mode. The determination occurs by increasing the current in the phase when one of the phase transistors is closed (section s, Fig.6). To avoid large values of the reverse moment when the phase transitions to the generator mode, current reduction is applied (minimum current sufficient for switching) before determining the position of the rotor. Here, the phase is turned off at the time of reduction t _ed. followed by a decrease in current to a value that is less than the operating current, but more than the threshold necessary to ensure satisfactory switching. When this current is closed through a power source (not shown) AIN 1, and it flows in the direction opposite to its EMF (section m, Fig.6). At the moment (t _open + t _close ), the windings are short-circuited, while the current continues to slowly decrease (section s) until the switching time t _com. matching the teeth of the machine, after which the current increases (generator mode). Having detected this increase in current, the control system 9 turns off the transistors of the inverter 1 and provides the final current drop (section w).

The accuracy of determining the phase switching moments with this control method directly depends on the cyclic polling of the phase current sensors 3 and the response time of the control system 9. In the control system 9 based on the sixteen-bit microcontroller C167 / ST10, the channel conversion time of the analog-to-digital converter is 10 μs. Thus, the cyclical updating of phase currents and the impact on the control object reaches 50 μs, which is about 2 el. hail at the optimum speed. In addition, it is necessary to allocate a measuring section to determine the moments of transition to the generator mode, in which one of the phase transistors must be in operation, which leads to insignificant underuse of the machine in time.

A block diagram of a combined sensorless control algorithm is shown in Fig.7. In blocks 10-14, the position of the rotor of the motor is determined and, depending on the direction of the given rotation, the optimal phase is turned on. In the phase, which must be switched on next, test pulses are supplied and at the same time they begin to measure the engine speed (blocks 15-17). At the moment of switching on the next phase (1 / 6T), where T is the phase period, the rotation speed n is measured. After 1 / 6T = t shut _. the phase is initially switched off and test pulses are supplied to the next incoming through 1 / 6T = t _open. into the work phase. In block 18 are constantly monitoring the engine speed n. If the frequency reaches n _gene. , there is a transition to a motor-generator algorithm of sensorless control. At time t _ed. they analyze whether the phase turns on or off (blocks 20-24). If the phase turns on, then through the interval t _com. turn on the next phase and update the speed values (blocks 18-21). If the phase turns off, then at time t _close. close one of the phase transistors (block 25), if both were open, and constantly monitor the sign of the derivative di _f / dt (block 26). When changing the sign in block 27, the second phase transistor is closed and the current speed n is measured (blocks 28-29). In block 30, an analysis of the engine speed is performed. If the frequency has decreased to n _gene. , then there is a transition to the starting algorithm for controlling the induction motor.

The advantages of this method include the following:

- no additional hardware is required in the power part of the drive and in the control system;

- It is possible to accurately determine the position of the stationary rotor;

- sustainable ID management over the entire speed range;

- the use of phase current correction algorithms to reduce ripple moment ID;

- entry into traction mode with coasting, i.e. with a rotating engine.

Using the proposed method can improve the reliability of controlling the induction motor in the entire range of rotational speeds and the efficiency of the electric drive due to the simplification of its design due to the refusal to use voltage sensors and temperature sensors used in the prototype.

Claims (1)

A method of controlling an induction motor, in which a tabular dependence of Δi _f on the position (angle of rotation) of the rotor, the dependence of the sequence of phase switching with the forward (forward) and reverse (reverse) direction of rotation of the rotor is pre-recorded in the memory of the control system, the parameters are measured and compared with tabular, they supply current packages, determine the optimal working phase according to the table of the sequence of phase switching at zero speed according to the ratio of the amplitudes of current packages of fixed duration all of the phase winding and the predetermined direction of rotation, characterized in that the moments of the start of formation current is determined as a function of current amplitude parcels, the speed of 0 to n _gene.
t _open = f (Δi _{f max} ), where
Δi _{f max} - the largest current package in the idle phase;
t _open - the moment of opening the current phase, measured by the number of clock cycles of the microprocessor timer (1 clock is 0.8 μs), a fixed duration and frequency, limited by the inductance of the inductor motor winding, the operating frequency of the transistors of the autonomous voltage inverter and the speed of the control system, and the moments when the current is supplied to the phase determine from the moments of opening the current and previous phases

where t is _closed - the moment of closing the current phase;
t _open - the moment of opening the current phase;
t _{open 1} - the moment the current switching starts in the previous phase winding;
and at rotation frequencies n> n _gene. determine the moments of the end of the current supply to the phase windings as a function
t _close = f (di _φ / dt),
where di _f / dt is the derivative of the phase current upon transition to the generation mode;
and the moments of the beginning of the formation of current in the phase are defined as

where: t _close - the moment of the end of the current supply to the phase windings of the previous phase;
t close ₁ - the moment of the end of the current supply to the phase windings of the current phase.

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